//AC

#include<stdio.h>

//#define FILEIO 1

int main() 
{ 
	float sum=0;
	float temp=0;
	int i;

#ifdef FILEIO
	freopen("in.txt","r",stdin); 
	freopen("out.txt","w",stdout);   
#endif
		sum=0;
		temp=0;
		for(i=0;i<12;i++)
		{
			scanf("%f",&temp);
			sum+=temp;
		}
		printf("$%.2f\n",sum/12);

#ifdef FILEIO
	fclose(stdin);
	fclose(stdout);
#endif
	return 0; 
} 
